19. Adiantum flabellulatum Linnaeus, Sp. Pl. 2: 1095. 1753.
扇叶铁线蕨 shan ye tie xian jue
Adiantum amoenum Wallich ex Hooker & Greville; A. fuscum Retzius.
Plants terrestrial, 20-45 cm tall. Rhizomes erect, short, scales dense, yellowish to brown, glossy, linear-lanceolate, margins entire. Fronds clustered; stipe black-purple, glossy, 10-30 cm, adaxially grooved with short stiff brown hairs inside, base covered with same scales as rhizome, distally glabrous; lamina pedately 2- or 3-dichotomously branched, flabellate in outline, 10-25 cm, middle pinnae usually longer, 1-imparipinnate; costae and stalks purple-black, abaxially glabrous, adaxially with dense, short, brown-red hairs; middle pinnae 1-pinnate, linear-lanceolate, 6-15 × 1.5-2 cm; outer pinnae similar but slightly shorter, up to 5 cm; pinnules 8-15 pairs per pinna, alternate, horizontally spreading; stalk 1-2 mm; blade below middle ± uniform in size, dimidiate-semi-orbicular when fertile, rhomboid when sterile, 6-15 × 5-10 mm, thinly leathery, green or dark brown, both surfaces glabrous, base broadly cuneate or flabellately cuneate, inner and lower margins straight and entire, outer and upper margins subrounded or rounded-truncate, fertile parts shallowly sinuate, segments entire, sterile parts denticulate; distal pinnules similar but slightly smaller; terminal pinnules obovate or flabellate, equal to or slightly larger than lower pinnules; veins multidichotomously forked and reaching margins, visible on both surfaces. Sori 2-5 per pinnule, horizontal, at upper and outer margins of segments; false indusia dark brown, semi-orbicular or oblong, glabrous, upper margins flat and straight, entire, persistent. Perispore indistinctly granular. 2n = 116.
Acidic red and yellow soils in open areas; 100-1100 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [India, Indonesia, Japan (including Ryukyu Islands), Malaysia, Myanmar, Philippines, Sri Lanka, Thailand, Vietnam].
The whole plant is used in traditional Chinese medicine and has a variety of uses. The plant is an indicator of acidity, growing on red and yellow soils with a pH of 4.5-5.
The name "Adiantum chinense" was a pre-Linnaean name introduced by Plukenet and recorded by N. L. Burman (Fl. Indica, 236. 1768) as a synonym of A. flabellulatum.